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fender
02-26-2008, 03:10 AM
Okay, since the board has been relatively quiet I'll show some pictures of my humble project. This is actually my "practice" locomotive; the main event is a 1.5" scale mikado. I figure that if mistakes are to be made, I'll make as many as possible on this. So far I've been pretty successful! :D

The original was a 12-ton 3' gauge locomotive built in the 1930's for a sugar cane plantation in Louisiana. As you can tell from the photos, it was very strongly influenced by steam locomotive construction practices, with equalized axles and a lead truck. (Note that Davenport called it a 2-4-0.) It also sported a bell and a whistle!

My version will be battery-powered, 7.5" gauge, 2.5" scale. The frame is flame-cut from 1" plate (the original had 5" thick frames!). The coupler pockets are cast in aluminum using a lost-foam method in my "driveway" foundry. The wheels are turned from 1" steel plate. So far, the only commercial parts are the bearings, chain, sprockets, and fasteners. Currently I'm working on the pony truck, which will use heart-shaped rockers.

Dan Watson

mdainsd
02-26-2008, 04:56 AM
Okay, since the board has been relatively quiet I'll show some pictures of my humble project. This is actually my "practice" locomotive; the main event is a 1.5" scale mikado. I figure that if mistakes are to be made, I'll make as many as possible on this. So far I've been pretty successful! :D

The original was a 12-ton 3' gauge locomotive built in the 1930's for a sugar cane plantation in Louisiana. As you can tell from the photos, it was very strongly influenced by steam locomotive construction practices, with equalized axles and a lead truck. (Note that Davenport called it a 2-4-0.) It also sported a bell and a whistle!

My version will be battery-powered, 7.5" gauge, 2.5" scale. The frame is flame-cut from 1" plate (the original had 5" thick frames!). The coupler pockets are cast in aluminum using a lost-foam method in my "driveway" foundry. The wheels are turned from 1" steel plate. So far, the only commercial parts are the bearings, chain, sprockets, and fasteners. Currently I'm working on the pony truck, which will use heart-shaped rockers.

Dan Watson


Thanks for sharing, that looks like one well built locomotive in the making. please keep up the flow of information on progress.

pockets
02-26-2008, 12:17 PM
Yes, thanks for sharing. I have a soft spot in my heart (head?) for critters and will enjoy watching this project.

Greg B.

Bill Shields
02-26-2008, 11:58 PM
You must be slipping...

You are supposed to DRINK the beer, not photograph it.

At least it's good beer.....

fender
02-27-2008, 12:57 AM
Bill,
That is my standard reference item for scale. Everybody knows how big a can of beer is, right? Or does it not translate to land of Oz?
Dan

Bill Shields
02-27-2008, 04:36 PM
OBVIOUSLY...

you have never been subject to the 'bet you cannot drink a 6 pack of.." with the Foster's liter cans....

tomc
02-27-2008, 05:18 PM
I am curious on how you plan on driving the wheels from the engine/transmision? I expected to see one more sproket on an axle. What's your plan?

Tom C.

fender
02-27-2008, 07:42 PM
Tom,
That was my original plan, but someone suggested that the main drive chain could go around three sprockets, (the third smaller sprocket will be on a jackshaft) which eliminates an extra chain from the drive. I'll post a rough sketch tonight.
Dan

watt-steam
02-27-2008, 11:42 PM
Hey Dan that little Davenport will be a nice one. Lookin good.

One thing to keep in mind about sprocket layouts is you need as much wrap of the chain around each sprocket as possible. 180 degrees is great. 90 degrees is about minimum. If you have to add idler sprockets to get better wrap on the driver and driven ones, to drive a chain between two shafts as you show in the pix, be sure to put the idler on the slack side of the idler or the idler bearing will wear fast.

fender
02-27-2008, 11:51 PM
Tom,

Here's a crude sketch of the drive design. By looping the main drive chain around a smaller sprocket on the jackshaft, I can eliminate the extra sprocket on one of the axles and an extra chain, as well as provide a means of tensioning the chain. I want to avoid having the lower chain "droop" and possibly catch on the rails of turnouts or crossings (or drag in the dirt!).

I'll probably have to experiment with different size sprockets on the motor shaft to get the speed I want from the loco. This supposed to be a switcher/hauler, not an express loco. Top speed per Davenport specs was 13.6 m.p.h.! :rolleyes:

Dan

emccamey
02-28-2008, 01:53 AM
Dan,

Just Calculate for your design (sample only provided):

You'll likely want to have top end at max of 2.5 MPH real speed. (I know a faster scale speed than your prototype - but you have to make some adjustments).

Thats (about) 5289 * 2.5 / 60 *12 = 2640 inches per min.
with 5" wheels thats' (about) 2640 / 15.7 = 168 RPM max axle RPM.

If the axle sprockets are 36 teeth: 168 x 36 = 6048 RPM
If the small jack shaft sprocket is 9 teeth: 6048 / 9 = 672 RPM
If the large jack shaft sprocket is 36 teeth: 672 x 36 = 24,192 RPM
If the motor sprocket is 9 teeth: 24,192/ 9 = 2,788 RPM of motor

Electric field wound and perm mag DC motors are avialable in the 2200 - 2800 RPM ranges - so you're good to go.

40 and 41 chains can have 36 and 9 sprockets easily found.

You can choose your motor, chain size and avialable sprockets selection to back into the needed parts. (You can also control motor speed electrically to reduce the max RPM - but you'll want it to be close the motor design for power efficiency.

Been there and done it. Work the calculations then do the physical mounting design with the selection of components. You have the room to develop what you need - I didn't, and had to reduce motor torque and speed with use of electronic controls. Electronic speed reduction will drive amperage draw up and reduce time between charges, so design for close to motor speed.

See my: http://www.coslar.us/FA1.html

Bill Cody
02-28-2008, 02:20 AM
Shouldn't you set-up your drive system to run about 10 MPH wide open? With a 10 MPH maximum you can maintain 7 MPH without running wide open. Seven MPH is the speed limit on the SVLSRM and you should be able to maintain that speed to keep up with traffic on the main line. It is only common courtesy not to be a rolling road block on the main line. Bill

emccamey
02-28-2008, 02:50 AM
Bill,

About 7 MPH would be my assumption for a main road locomotive. But Dave is designing and providing a yard locomotive. And one very large hunk of metal the frames appear to be. If Dave intends to operate the Davenport out on the main - then getting closer to 7-8 MPH capability would be advised and get the axle RPM up to about 500 to 575 RPM would work out well.

Being an aside though, I'd find that 7 MPH for a 7-1/2" gage track as a 'normative' is too fast anyway. My FA1 could actually clock in at about 13 MPH - but I'll tell you this, I DIDN'T like going that speed at all, and have reduced it to no more than 8 MPH with a top end variable resistor speed control in the controller.

Track speed is as much a function of the track condition and the avialable geography and geometry of visibility and distance. Some tracks can handle and allow for 8-10 MPH with out a problem, and some - 5 MPH is way too fast.

You do need additional 'power' for longer grades and for longer trains, which when running light can allow for faster speed.

It's all a 'design' and 'purpose' choice. I've been behind one of those Cli-Shay bottle necks and yes, it's sometimes a frustration, but it was moving a lot faster than a scaled speed of it's prototype.

Bill Cody
02-28-2008, 04:38 AM
He may be building a yard loco but I feel sure it will not stay in the yard, it will end up on the main. At 2.5 MPH maximum speed it will be a rolling roadblock and cause much consternation among the other engineers. You mention being caught behind a Clishay. Isn't the Clishay designed for use in the woods like the regular Shay? Don't quote me but wasn't the Shay designed with a maximum sustainable speed of 10-12 MPH? 12 MPH divided by 8 = 1.5 MPH as scale speed. The Shays that Ken Schroeder supplies casting/prints for will run with most rod engines so they are running well above "scale speed". As a concession to the other engineers we must design/build our locomotives with the capability to run at normal track speed.
Bill

fender
02-28-2008, 04:40 AM
Thanks for everyone's comments. On the matter of speed and motor, I have a permanent magnet motor I bought on ebone so at this point I'll have to experiment with various sprocket sizes to get a reasonable speed. I was joking about the top speed of the prototype, for to scale that exactly would be a bit slow. I've even thought about making the motor mounting adjustable so that I could quickly change out the motor drive sprocket according to track conditions, higher gear ratio for hilly track, lower ratio for more level track. (Also, higher ratio for beginners and kids!)

I'm interested in Watt's comment about the "wrap" of the chain around sprockets.....maybe I should revise the design so that the smaller sprocket is above the chain instead of below it. That would give more "wrap" of the chain without introducing idler sprockets ???

Dan

Bill Cody
02-28-2008, 07:50 AM
Dan: Glad to hear you are going to make the max speed something realistic for use on the main line. I don't think there is anything that frustates me more than to be stuck behind an extremely slow running on the main line. I feel you should run at track speed if there are other engines/trains on the track. It was mentioned earlier that different tracks reqired different speed limits. Very true Same holds true for roads for cars. I seem to remember a situation on car speed limits when I lived in Southern California in the late 40s that said you could get a speeding ticket even while driving at a speed less than posted. Had something to do with weather, traffic,visibility and road conditions. Don't remember exactly, after all its been 58-59 years ago and I'm getting CRS??? Bill

watt-steam
02-28-2008, 02:35 PM
Dan, I made a sketch showing a couple ideas about chain run layouts, hope it helps.

(also hope it attaches OK and you can view it)

Watt

pkastagehand
02-28-2008, 02:42 PM
That is what I thought you had in mind from your earlier post. But as Watt-Steam pointed out, 90-180 degrees of wrap is what you want. With your setup as shown you will risk slippage and will incur more wear on that drive sprocket even if it doesn't slip because the force will be on fewer teeth at any given moment.

Paul

mdainsd
02-28-2008, 02:51 PM
Dan: Glad to hear you are going to make the max speed something realistic for use on the main line. I don't think there is anything that frustates me more than to be stuck behind an extremely slow running on the main line. I feel you should run at track speed if there are other engines/trains on the track. It was mentioned earlier that different tracks reqired different speed limits. Very true Same holds true for roads for cars. I seem to remember a situation on car speed limits when I lived in Southern California in the late 40s that said you could get a speeding ticket even while driving at a speed less than posted. Had something to do with weather, traffic,visibility and road conditions. Don't remember exactly, after all its been 58-59 years ago and I'm getting CRS??? Bill

California still has that, it is called the "basic Speed Law" and paraphrased, it says what you said. You cannot drive faster than conditions allow for, regardless of posted limits. Interesting side note: A friend of mine is a CHP officer. I asked him what they did about people driving while reading or text messaging. He told me that when he stopped someone for doing this they would generally reply "hey! its not against the law", to which he would reply, "please explain to the judge what speed you think would be safe while reading the paper" Basic Speed Law to the rescue.

pkastagehand
02-28-2008, 02:51 PM
I'm interested in Watt's comment about the "wrap" of the chain around sprockets.....maybe I should revise the design so that the smaller sprocket is above the chain instead of below it. That would give more "wrap" of the chain without introducing idler sprockets ???

Dan

That would give slightly more wrap, though maybe not enough to make a difference. It would also however cause a loosening of the chain as axles move up and down. The higher above the axle centers you go, the more this slackening effect (up to a point of course).

pkastagehand
02-28-2008, 03:05 PM
I started a 4 wheel switcher awhile back. I've since switched back to my Pennsy A3 in 3/4" so it is on hold for now. Here is my cad sketch of it. Freelance design. Hopefully it will be "diesel"-electric using a gas engine to drive a generator which will drive the electric motor which will drive the wheels.


http://www.hope.edu/academic/theatre/anderson/img/switcher.jpg

Paul

fender
02-28-2008, 03:34 PM
Dan, I made a sketch showing a couple ideas about chain run layouts, hope it helps.

(also hope it attaches OK and you can view it)

Watt

Viewability is fine, thanks.
I had another idea, maybe I should learn something from Caterpillar:
http://www.cat.com/cda/layout?m=163632&x=7&f=151869
The chain I'm using is grossly oversized for the requirement, so I don't think wear is going to be a problem in any event.
Dan

toolman1951
03-15-2008, 10:48 AM
Dan
In between working on my A3 Switcher, I too am building an Electric Loco. I found some rough plans on the net somewhere. I will look similar to a typical small Diesel switch engine. 7-1/2" gauge with a couple riding cars for my grandson and me. I needed something to get on the rails quick because I realize the A3 is going to be a long term project for me. Hope to see more updates on this project from you. Looks good!
Toolman

fender
03-15-2008, 11:02 PM
Toolman,
I don't have any grandchildren yet, but that is definitely a consideration. I've been a live steam "groupie" for more years than I care to admit. And no loco of my own to run! So this project is a way to remedy that problem.
P.S. I rode on the prototype Davenport back in the late 1960s on a sugar cane railroad, which helps for motivation.
Dan